Prokaryotes: The big picture


  • ‘Prokaryotes’ are not a monopheyltic group
    • Kingdoms Bacteria & Archaea; each with unique traits
    • most species diverse groups on Earth


  • Diversity of ways of making a living
    • sources of energy to make ATP
    • heterotrophs
    • autotrophs (photosynthesis)


  • Co-evolution with the planet and other organisms
    • oxygen poor to oxygen rich world
    • extremeophiles (temperature, pH, salt,etc.)
    • prokaryotes are most abundant organisms on Earth!

Prokaryotes do it all! (review Table 27.1)


  • Sources of carbon
    • autotrophs (make themselves)
      • chemically
      • light
    • heterotrophs (get from others)


  • Energy for ATP (no mitochondria)
    • sunlight
    • organic molecules
    • inorganic molecules


  • Lifestyles reflected in extensive genetic diversification


Picture: Iron-oxidizing bacteria are chemoautotrophic bacteria that derive energy by oxidizing ferrous iron

Prokaryotes need nitrogen and may need oxygen

  • Metabolism varies with respect to oxygen
    • use for cellular respiration
    • or poisoned by it!
    • some can extract chemical energy from nitrite or sulfate


  • Nitrogen is essential for production of amino acids
    • prokaryotes less limited in obtaining nitrogen


  • Some bacteria convert atmospheric nitrogen (N2) into usable forms
    • termed Nitrogen fixation


  • Picture: Bacteria work together
    • photosynthesis and N fixation

Metabolic cooperation leads to Biofilms


Biofilms are living communities that allows microorganisms (such as single-celled bacteria) to behave as a group


  • Fossil evidence of biofilms dates to about 3.25 billion years ago


  • More than 75% of human infections are thought to be related to the presence of microorganisms in the form of biofilms
    • on the surface of tissues or medical devices
    • dental plaque!


  • Biofilms are not exclusive to prokaryotes but include them
    • green film on pond rocks

Rapid reproduction leads to high genetic diversity

  • Rapid reproduction and large populations leads to many mutations
    • not through sexual reproduction
    • 2 x 10^10 new E.coli cells in human intestine each day
    • possible for millions of mutations each day
    • infant microbiome diversifies rapidly based on environment..

Reproduction in prokaryotes: Binary fision


  • Asexual: daughter cells identical to parent
    • rapid reproduction
    • not sustainable!
    • not great for genetic diversity


  • Mutations add to diversity but are still rare


  • Horizontal gene transfer increases diversity:
    • transformation =
    • transduction =
    • conjugation =

Genetic Recombination: Transformation

Utilizing transformation for science advancement…

  • Manipulating DNA sequences in vitro, creates recombinant DNA molecules that have new combinations of genetic material


  • Recombinant DNA is then introduced into a host organism
    • If the DNA comes from a different species, the host organism is considered to be transgenic.

Genetic Recombination: Conjugation (mechanism unresolved)

Many R plasmids carry genes for antibiotic resisitance



  • Many species of bacteria carry genes that code for enzymes that destroy/hinder antibiotics
    • tetracycline, ampicillin


  • Genes often carried in plasmids (R plasmids)


  • R plasmids have genes that encode for pili (conjugation bridge)
    • enable conjugation
    • resistance genes can spread quickly

Prokaryotes are incredible diverse


  • Acutally a big assumption!
    • only 16,000 described


  • Genomes are super diverse because of horizontal gene transfer


  • Bacteria: prokaryotic species most commonly known
    • from pathogens to yogurt


  • Archaea: share traits with bacteria and eukaryotes
    • earliest ancestors in extreme environments

Prokaryotes matter: Cyanobacteria


  • Cyanobacteria: first evidence ~3.5 bya
    • blue-green algae
    • aquatic and photosynthetic
    • use chlorophyll


  • Photosynthesis evolved independently in distant groups
    • mono, para or polyphyletic?
    • cyanobacteria are a monophyletic group


  • Eukaryotes acquired photosynthesis by engulfing cyanobacteria!

Prokaryotes matter: Great Oxygenation

Banded iron formation (2.4 bya) the result of oxygen, dissolved iron and sea water

Prokaryotes matter: Oxygen Revolution

Prokaryotes matter: Chemical Recycling in Nature

Prokaryotes matter: Species Interactions

Prokaryotes matter: Microbiomes

Helps with digestion, destroys harmful bacteria and helps control your immune system.

Prokaryotes matters: Humans